[unreadable] VisEn Medical, Inc. is proposing to develop novel targeted imaging probes for molecular imaging in small animals and human applications. The technology platform to be investigated in the application is based on novel iron oxide nanoparticles developed for target specific magnetic resonance imaging (MRI). VisEn Medical, Inc. has developed a class of novel magnetic nanoparticles, characterized by 1) extremely high stability achieved through "pseudocaging", 2) high magnetic relaxivity, 3) high efficiency targeting achieved through multivalency coupling of small molecule targeting ligands and 4) detectability by optical means through conjugation of high quantum yield near-infrared fluorochromes. These materials (pseudocaged nanoparticles or PNPs) are expected to have superior characteristics compared to dextran coated iron oxide nanoparticles currently in clinical and preclinical use, and are specifically designed to lead to the next generation of MRI agents with molecular specificity. The overall goal of Phase I of this proposal is to develop the technology platform that will enable development of the next generation of targeted PNPs for MRI. Specifically, we will systematically characterize three lead PNPs differing in size, characterize their physicochemical properties and test their cellular behavior. [unreadable] [unreadable]